Single print element print carrier with self-contained selection function

ABSTRACT

A carrier for a printer, having a single type element, is disclosed. The selection apparatus contained within the carrier is one whereby only a rotary power force plus control signals need be introduced into the carrier. The selection apparatus is comprised of barrel cams having a plurality of channels formed into the periphery of the barrel cams to cause lateral displacement thereof on their drive shaft. The lateral displacement of the barrel cams is converted into a linear motion which is in turn transmitted and converted into rotary motion to position the type element about its rotate and tilt axes. The controls for transmitting signals to the carrier are pneumatic and the pneumatic impulses received by the carrier logic block and actuator blocks activate mechanical latches to insert selector pins into the grooves of the barrel cams. A dual rack and single pinion arrangement is disclosed to convert the linear motion to rotary motion of the type element.

United States Patent [191 Shakib 1 SINGLE PRINT ELEMENT PRINT CARRIER WITH SELF-CONTAINED SELECTION FUNCTION [75] Inventor: Iraj D. Shakib, Lexington, Ky.

[73] Assignee: International Business Machines Corporation, Armonk, NY.

[22] Filed: June 29, 1973 [21] Appl. No.: 375,277

[52] US. Cl. 197/18; 197/55; 197/82 [51] Int. Cl B41] 23/04 [58] Field of Search 197/16, 18, 19, 20, 49,

[56] References Cited UNITED STATES PATENTS 2,774,816 12/1956 Yost 197/49 X 3,151,547 10/1964 Hornauer et a1 197/49 X 3,302,765 2/1967 Hickerson et a1 197/18 X 3,455,428 7/1969 Shida et a1. 197/18 X 3,572,486 3/1971 Hebel et a1. 197/18 X 3,625,331 12/1971 Waldenburger 197/55 X 3,666,070 5/1972 Schaefer 197/18 1 July 1,1975

Primary ExaminerEdgar S. Burr Assistant Examiner-R. T. Rader Attorney, Agent, or Firm-Laurence R. Letson [57] ABSTRACT A carrier for a printer, having a single type element, is disclosed. The selection apparatus contained within the carrier is one whereby only a rotary power force plus control signals need be introduced into the carrier. The selection apparatus is comprised of barrel cams having a plurality of channels formed into the periphery of the barrel cams to cause lateral displacement thereof on their drive shaft. The lateral displacement of the barrel cams is converted into a linear motion which is in turn transmitted and converted into rotary motion to position the type element about its rotate and tilt axes. The controls for transmitting signals to the carrier are pneumatic and the pneumatic impulses received by the carrier logic block and actuator blocks activate mechanical latches to insert selector pins into the grooves of the barrel cams. A dual rack and single pinion arrangement is disclosed to convert the linear motion to rotary motion of the type element.

7 Claims, 26 Drawing Figures KEYBOARD SIGNAL GENERATOR SHEET LOGIC BLOCK FIG.

ACTU BL Ebnu T LATCHES 1 11 DEAD KEY ND PRINT RACK SWITCH FNENTESJUU FIG. 10

Tu a: 9 60 SHEET FIG. 14

FIG. 15

SHEET FIG. 16

FIG. 17

PATENTEUJUU 3.892.304 sum 10 FIG. 21

HEET FIG. 25

FIG, 24

1 SINGLE PRINT ELEMENT PRINT CARRIER WITH SELF-CONTAINED SELECTION FUNCTION BACKGROUND OF THE INVENTION Single element typewriters and printers have been known generally for quite some time. The fact that a single element typewriter with a fixed carriage requires a moving print carrier has in the past required extensive interconnections between the keyboard and the print carrier. The interconnection technique has primarily been through pulleys, tapes, cables, and the like which decode through a mechnical linkage a keyboard input and transmit that information to the carrier by means of differential lengths of tape or cord which are taken up through the movement of pulleys thus causing the type element to rotate and tilt the appropriate amount to position the desired character at the print point. The requirement for extensive mechanical interconnections between the main frame of the typewriter and the rotate-tile apparatus on the print carrier requires a very accurately manufactured side frame or power frame for the typewriter in addition to exceedingly accurate positioning of components on that power frame. Such tight tolerance requirements increase the cost of manufacture and require extensive adjustments to make the typewriter or printer work properly. Also, during the manufacturing process it is necessary to build up each power frame piece by piece to produce the typewriter and then interconnect the appropriate decoding linkages and mechanisms with the print carrier. These expensive manufacturing techniques and adjustment requirements not only are tedious but provide additional possibilities for maladjustment.

OBJECTS OF THE INVENTION It is a primary object of this invention to provide the capability for modular assembly and adjustment of a single element typewriter.

It is an additional object of this invention to minimize the interconnections between the keyboard and print carrier of a single element typewriter.

It is a further object of this invention to ease the manufacture and adjustment of the selection mechanisms for a single element typewriter.

It is another object of this invention to eliminate mechanical control interconnections between the keyboard and the printer carrier of a single element typewriter.

SUMMARY OF THE INVENTION The foregoing objects are accomplished by the inclusion of the entire selection mechanism in the print carrier and the connection of the keyboard to the selection mechanism through either electrical or pneumatic means. The print carrier is provided with a translator to translate or decode the input signals which are in the form of pneumatic or electromagnetic signals and the decoding of those signals such that the keyboard originated output is converted into a plurality of signal pulses one corresponding to rotation of the type element. a second corresponding to the tilt of the type element. a third corresponding to a print/no print condition and a fourth corresponding to rotate direction. This converts the keyboard output to a set of signals capable of interpretation at the carrier and conveyed thereto through either pneumatic tubes or electrical conductors. This eliminates the rotate and tilt bands,

LII

the associated pulleys, together with the mechanical decode. rotate and tilt mechanisms necessary to decode the keyboard originated logic signals of the prior art. The tilt and rotate signals are then fed to latches which unlatch selector pins and allow the pins to drop into a barrel cam. The rotation of the rotate barrel cam causes alateral translation thereof with a corresponding lateral translation of a follower linkage which is part ofa linear to rotary motion convertor. The linear to rotary motion convertor translate the relative displace ment of the barrel cam into a rotary motion of the keyboard thus selecting the column of characters desired. Similarly, rotation of the tilt barrel cam results in lateral displacement of the tilt barrel cam as a result of its rotation and engagement with a fixed selector pin and is converted through bell cranks and linkages to a pushpull action causing the tilt ring of the print element rocker assembly to rotate about a horizontal axis thus positioning one of the characters within the previously selected row in the proper position for printing.

Continued rotation of the print shaft causes a plurality of cams to interact with detenting mechanisms for final head alignment and the activation of the print rocker by the engagement of the rocker arm through a follower wheel to the print cam. Upon the completion of the impacting of the typehead into the platen, the type element or print head is returned to its home position, by the barrel cams rotation and subsequently restores the selection pins to their latched condition.

By the inclusion of the character selection mechanism within the carrier, interconnection between the keyboard and power frame with the carrier are eliminated except for data signal lines and the print shaft. The mechanical linkages necessary to control prior art selection mechanisms and then transmit the output of those mechanisms to the carrier are eliminated simplifying manufacture, maintenance and enhancing the modular construction nature of the typewriter.

A better understanding of the invention may be secured from a reading of the detailed description and viewing of the attached figures in the drawing.

DRAWING FIG. 1 is a single element typewriter having a carrier of the type disclosed herein.

FIG. 2 is a left front perspective of part of the carrier of the typewriter illustrated in FIG. 1.

FIG. 3 is a partial simplified end view of the print cam and print rocker of the carrier of FIG. 2.

FIG. 4 illustrates the selector pin latch assembly together with the barrel cams in their home position.

FIG. 5 is a section view along 5-5 in FIG. 4.

FIG. 6 illustrates the escapement linkage and the escapement cam carried within the carrier.

FIG. 7 shows the no right control for controlling the cam follower of the print cam.

FIG. 8 illustrates a partial top view of the escapement cam and follower mechanism together with the velocity and no print control.

FIG. 9 illustrates the selection rack and pinion together with the reset control and detenting cam follower and detenting mechanism of the print carrier.

FIGS. 10, 11, I2, and 13 are respective end and section views of the barrel cams.

FIG. 14 Isa plane view of the rotate selection cam.

FIG. 15 is a cam diagram of the rotate cam of FIG. 14.

FIG. 16 is a plan view of the tilt control cam.

FIG. 17 is the cam diagram for the tilt barrel cam of FIG. I6.

FIG. [8 is an exploded view of the motion conversion and transmission portion of the selection apparatus.

FIG. 19 is perspective view ofa single selector pin selector control and a partial view of a single track branched groove barrel cam.

FIG. is a schematic block diagram of a suitable control network to provide signals to the carrier of FIG. 2.

FIG. 21 is schematic of the single selection pin embodiment with the cam associated therewith stretched out to a cam diagram.

FIG. 22, 23, 24 and are sections of the cam of FIG. 21 showing depth of various grooves at various cam stations.

FIG. 26 is a plan view of the cam represented by the cam diagram of FIG. 2].

DETAILED DESCRIPTION To provide the printing function of a typewriter such as a single element printer or typewriter, a carrier 10 is provided within the typewriter 12. This carriage is translatable across the print line of typewriter 12 on print shaft 14. The print shaft 14 is a rotatable shaft which provides the driving forces to the carrier 10 to cause activation of single print element 16. The control signal for the selection of the character on print element 16 are transmitted from keyboard 18 to the carrier 10 by means of control signal lines 20. Upon re ceipt of appropriate signals transmitted through lines 20 to carrier 10, type element 16 is rotated and tilted to present the desired character in position opposite 22 such that when the type element 16 is impacted into platen 22 a printing operation occurs and a character or other symbol is deposited on page 24.

To provide the input to the carrier 10 so that selection and printing may occur in the carrier 10, a keyboard 18 is provided. Keyboard 18 interacts with a keyboard signal generator 26. Keyboard signal generator 26 may take the form of pneumatic valves actuated by mechanical motion of the keyboard or it may be an electrical signal generator which is activated as a result of the mechanical operation of keyboard 18. Keyboard generator 26 provides the capability of producing plurality, n, of output signals. The signals generated by the keyboard signal generator are transmitted to a logic block 28 which then converts these signals into a series of m processed signals which are then outputed from the logic block 28 into an actuator block 30. The actuator block 30 receives the logic block outputs and converts these logic block outputs into a binary coded output of the keyboard key depression. The actuator block converts the pneumatic or electrical signal into a mechanical movement. In this case, the mechanical movement is the control of the rotate and tilt by selection latches 32-4I. Also outputed from the logic block, but not transmitted through the actuator block are additional signals representing such functions as rack switch, no print, and dead key. The utilization of these signals, directly by the mechanisms of the carrier, will be described in detail below.

As stated earlier, the keyboard signal generator 26 may be either pneumatic or electronic or any other technique which allows the conversion ofa mechanical physical motion of the keyboard 18 to be converted into a series of binary signals. These signals are then passed into a logic block 28. The function of the logic block is to convert a small number of signals from the keyboard generator 26 into a larger more comprehensive series of signals m which are outputed by the logic block and directly used in a signal to mechanical motion convertor or actuator block 30. Also, there are signals outputed from the logic block 28 which are used directly by the carrier I0 to control ancillary nonselection functions such as dead key, no print and rack switch.

In order to more fully understand the operation of the actuator block 30, which is a signal receiving means, reference is made to FIGS. 4 and 5. Actuator block 30, for sake of illustration, is shown as a pneumatic block in section view in FIG. 5 and in broken away view in FIG. 4 is made up of several components. The block member 32 is formed with a depression 34. This depression is sealed by flexible pneumatically distensible membrane 36 at points 38 in FIG. 5. Points 38 in fact are edge sealing regions as opposed to physical points. The chamber 40 formed by distensible membrane 36 and depression 34, is connected to the logic block through conduit 42. Conduit 42 provides a path to transmit signals from the logic block 28 into the chamber 40. In the case of pneumatically actuated systern, the depression of the keys of keyboard 18 provide a series of output signals from the keyboard signal generator 26. These signals are received by and decoded by logic block 28 to provide signals for the actuator block 30. The logic block 28, through the logic net work contained therein, provides an output signal in a pneumatic pulse form and absence of pneumatic pulses in the event that a tilt or a rotate function or both are required of the print element 16.

If a tilt or rotate is required to position print element 16 in its appropriate condition for subsequent impacting, a pressurized pulse of air is transmitted through conduit 42 and pressurizes cavity 40, as illustrated in FIG. 5. As the pressure in cavity 40 builds distensible membrane 36, exerts the corresponding pressure onto latch shoe 44. Latch shoe 44 is pivotally attached by pin 46 to a latch lever 48. Latch lever 48 is pivotally mounted on pivot point 50 and biased in a counterclockwise direction by biasing spring 52. Latch lever 48 is further provided with a latching surface 54. Also provided on latch lever 48 is an extending tab portion 56. Tab 56 extends into a ballsometer or a ball tube interlock 57 which provides a technique for preventing more than one latch lever 48 from being activated in response to a single set of rotate signals and likewise only one tilt latch member 48 may be activated by a single set of tilt signals. The ball tube interlock technique is well known and well disclosed as a keyboard interlocking technique in other U.S. patents, such as U.S. Pat. No. 3,086,635 to L. E. Palmer.

As a pulse is received through the conduit 42 and causes membrane 36 to force shoe 44 and latch arm 48 to rotate in a clockwise direction around pivot point 50, latching surface 54 disengages from latch notch 58 selector pin 60. Selector pin 60 is provided with a spring bias 62. Spring bias 62 is a compression spring tending to force selector pin 60 in a leftward direction in FIG. 5 and in a downward direction in FIG. 4. Selector pin 60 is provided with a flatened blade portion 64. This flatened blade portion 64 is adapted to engage with and ride in the selection groove -76 and 170-173 of the selection and tilt barrel earns 68, 168.

The selector pins 60 and their associated latches may be considered as selection means or positioning means as they provide selection of grooves and a fixed position for earns 68, 168 to rotate with respect to.

To convert the actuation of a latch arm 48 into a usable motion for the purpose of translating the print head about the tilt and rotate axis, the blade portion 64 of selector pin 60 engages its respective track in the rotate or tilt earns 68, 168 illustrated in FIGS. and 17. With respect to the rotate cam, illustrated in FIG. 15, there are a plurality of selection grooves 70-76. For the sake of clarity, the grooves are indicated with 70-76, however, the units of relative selection displacement or units of rotation of the head, is indicated by the unit digit of the reference numeral. For example, the groove labeled 70 is a zero displacement, home row or zero rotate condition. Groove 71 is a one unit rotate groove, groove 72 is a two unit rotate groove, and so on through groove 76 which is a six unit rotate groove. Groove 78 is the groove into which a follower is inserted to provide translatory motion to the follower as a result of the translational movement of the barrel cam 68. Each of the grooves 71 through 76 has a widened portion 80 to facilitate the entrance of selector pin blade 64 into the respective grooves. Rotate barrel cam 68 is coaxially, slideably mounted on keyed rotating shaft 82 by means of projections 84 on shaft 82 and mating recesses 86 in barrel cam 68. This mounting technique provides a capability for barrel cam 68 to rotate in response to the shaft rotation of shaft 82. It also allows for a coaxial translation of barrel cam 68 with respect to shaft 82 in response to the selecting or picking of one of the selector pins 60 and the dropping of the blade portion 64 into one of the selection grooves 70-76. The translatory motion is caused by the blade portions 64 being held in a fixed position and the cam rotating around the axis of the shaft 82 thus causing the cam to displace laterally in FIG. 4. Groove 78 of rotate cam 68 is an entirely circular groove which provides a recess for follower tab 88 to engage as seen in FIG. 9. The function of follower tab 88 together with follower 90 will be more fully discussed below.

Zero select groove 70 is likewise a circular groove with no radial dwells, rises, or falls. Engaged in cam groove 70 is a zero select homing pin 92, illustrated in FIG. 4. Homing pin 92 is spring biased by compression pin 94 thus exerting a force on the homing 92 to cause it to move downward in FIG. 4. This maintains engagement between pin 92 and zero rotate groove 70. Pin 92 remains engaged with groove 70 unless one of the pins 60 is released by its appropriate latch arm 48, and allows to engage its respective groove. In the event that one of the selector pins 60 is allowed to extend and engage its respective rotate groove 71-76 in cam 68, the cam will rotate and pass the pin until it reaches approximately 90 of rotation. At that time, as can be seen readily from FIGS. 15, the pin will deviate from a straight path and attempt to follow the track. Since the pin 60 is fixed and the cam 68 is coaxially slideable on shaft 82. the cam 68 will translate in response to the deviation of the respective groove from the straight course. This causes a direct translational movement of groove 78 and thus causes follower tab 88 and follower 90 to move therewith. Thus it can clearly be seen if the rotate grooves or selection grooves 71-76 are cut into cam 68 in such a way as to provide a proportional lincar displacement corresponding to one through six units of translational motion, the groove with the largest cam shift will thus be the six unit rotate while the groove with the smallest shift will be the one unit rotate. As the cam 68 rotates after the engaging of a pin 60 into one of the rotate grooves 71-76 and cam 68 begins it lateral translation. a radial as well as lateral camming surface 96, is displaced under homing and zero rotate pin 92, and thereby forces pin 92 against the biasing of spring 94 up the incline 96 onto external cylin drical surface 98. The zero rotate homing pin 92 remains cammed out of track until the rotation of the cam has been accomplished through approximately 270 of rotation at which time a complimentary reverse camming surface 99 acts to allow the pin to descend into its engaged position as the cam is returned to its zero displacement position. At approximately 3l5 of rotation, the home select pin is substantially returned to its operative depth and is ready for engagement with groove 70. At approximately 345 of rotation, home select pin 92 will be fully re-engaged with the track 70.

Referring now to FIG. 11, which is a cross-sectional view of rotate cam 68 in track 71, it can be understood how the blade portion 64 of a selector pin 60 can engage the track and be reset. The blade portion 64 of selector pin 60 is inserted into groove 71 at a point approximately at the 0 axis in FIG. 11. As the cam rotates in a counterclockwise direction progressively presenting an increasing degree position of the cam circumference to blade 64, the cam profile of the bottom of groove 71, forces the pin 60 and blade portion 64 radially outward during the rise and dwell portion of that camming action. As lobe I02 passes the 0 axis of FIG. 11, the radial distance from the center of shaft 82' to the rise 102 is sufficient to compress spring 62 on pin 60 and allow bias spring 52 to rock latch arm 48 in a counterclockwise direction thus engaging latching surface 54 with pin latching surface 58. As cam 68 continues to rotate lobe 102 terminates at approximately 345 of rotation thus allowing pin 60 to be positively latched by latch arm 48. At this time the cam has been rotated through one complete cycle of rotation and the cam has translated one unit of translation which will ultimately correspond to one unit of rotate. The selector pin 60 has been inserted into the groove 71, the selector pin 60 has guided cam 68 and has then raised out of the groove 71 and allowed to relatch in a retracted position. This has, at the same time, accomplished the camming of the zero rotate pin out of groove 70 up incline 96 into cylindrical exterior surface 98 down descending cam surface 99 and return to groove 70. A similar mode of operation is possible if any other cam groove is selected by the unlatching of the appropriate selector pin 60. The cam profile 100 and lobe 102 is identical for all the grooves 70-76.

Referring to FIG. 4, the rotate cam 68 is forced toward the right on shaft 82 as shaft 82 rotates.

Referring now to FIG. 9, follower tab 88 of cam follower 90 is engaged in follower groove 78. Follower 90 is slideably supported on shaft 110. Follower 90 includes a slot 112 for receiving rack tab 114. Rack tab 114 engages slot 112 to receive the translatory motion of follower 90 in response to the translatory motion of cam 68 transmitted through tab 88. Shaft is rigidly fixed into rocker 116 which is in turn pivoted upon a pivot pin 118. Rack tab 114 is rigidly attached to or formed into switchable rack 120. Rack 120 is pivotally mounted on and slideable on shaft 122 which is likewise carried by rocker 116. Cam follower 90 is likewise slideably mounted on shaft 122 as well as 110 as indicated earlier. Referring to FIG. 18. the bifurcated nature of rack 120 can be more clearly seen. Rack 120 has a dual arm arrangement with gear teeth formed in each arm. Rack 120 has gear racks 124 and 126. Each rack 124 and 126 is formed on a separate portion of overall rack 120. The respective racks 124 and 126 are angularly disposed such that when rack 120 is tilted as far as it can be displaced in one angular direction, one of the racks. for example, 124 will be co-planar with and engage the teeth on pinion 128. Pinion 128 is fixedly mounted on the lower ball socket shaft 130. Lower ball socket shaft 130 extends up through the yoke 132 to the lower ball socket 134 which is formed as a part of the lower ball socket shaft 130.

To provide the facilities for selectively engaging one rack of the two racks 124, 126 of switchable rack 120, a shifter tab 136 is formed into the non-used edge of rack 124. To provide the shifting movement and forces necessary to shift rack 120 to engage rack 126, a rack shift mechanism 138 is provided. Rack shift mechanism 138 is comprised of an actuator lever 140. This lever may be actuated by either pneumatic or electromagnetic means. For the sake of illustration, a pneumatic actuation mechanism will be described. referring to FIG. 9 and 18. The pneumatic actuation mechanism is comprised of a bellows block 142 with an input port 144. Formed into the underside of bellows block 142 and communicating with input port 144 is chamber 146 which is sealed with a distensible membrane 148. Engaging the atmosphere side of membrane 148 is bellows member 150. Bellows member 150 is pivotally mounted on and spring biased around pin 152 by spring 154. Rack switch lever 140 may be attached to or formed at a part of bellow member 150. The inflation of the bellows 138 will cause engagement between rack switch lever 140 and rack switch tab 136 causing rack switching or shifting around shaft 122 in a counterclockwise direction as viewed in FIG. 9.

To provide the resetting of the rack in its normal, home, minus rotate position with rack 124 engaging the teeth of pinion 128, a reset leaf spring 160 is provided. Reset leaf spring 160 is attached to rocker 162 which is pivotally attached to shaft 100. Extending from rocker 162 are follower arms 164 and 166 as viewed in FIG. 18.

In order to provide actuating inputs to follower arms 164 and 166, cam profiles are cut into the ends of ro tate cam 68. These cam profiles 77 and 79 can best be observed in FIGS. 12 and 13. Follower arm 166 is positioned to engage cam profile 77 when the home or zero rotate pin 92 is engaged with its homing track 70. As cam profile 77 in FIG. 13 is rotated under follower arm 166, the follower arm will ride up the cam profile 77 thus causing rack switch spring 160 to engage the lower portion of rack 120. As the rack 120 is engaged and forced upward by the continuing rise of follower arm 166 and its rotary action on rocker 162 and spring 160, the rack is forced to switch positions such that rack teeth 124 engage pinion 128 and rack teeth 126 disengage pinion 128. This switch position is maintained by overcenter spring 168. Overcenter spring 168 is attached to cam follower 90 which provides a tab 90'. The other end of the overcenter spring 168 is attached to a tab 120' formed onto the switchable rack 120.

Cam lobe 77 is positioned at a location such that when enlarged portions on the rotate cam 68 are presented to the blade 64 of selector pin 60, the highest dwell of cam 77 is under follower 166 thus causing rotation and transmission of force through rocker 162 and leaf spring or rack switch spring 160. Thus it can be seen that as the rotate cam 68 is positioned in its home or start position the rack switch cam follower 166 and the rack switch spring 160 act to always engage rack teeth 124 with pinion 128. This provides the capability of returning the rack 120 to a minus rotate condition upon the completion of each revolution of rotate cam 68.

The construction of rack switch bellows assembly 138 has been discussed above. When a plus rotate condition is desired, rack switch bellows assembly is pressurized through input port 144 leading to engage rack tab 136 causing rack 120 to switch thereby engaging rack 126 with pinion 128.

Inasmuch as rotate cam 68 only translates in one lateral direction during the first 180 of rotation of that cam, the engagement of rack 126 will create an opposite rotation of pinion 128 and lower ball socket shaft 130.

Cam follower arm 164 is positioned on shaft to cause rocker 162 and hence, rock switch spring 160 to rotate. The distance between follower arm 166 and 164 is equal to the cummulative distance equal to the length of cam 68 between cam surfaces 77 and 79 plus the distance which cam 68 will laterally translate when a selector pin 60 and blade 64 are caused to engage rotate slot 76 corresponding to six units of rotation. Cam 68 will translate on keyed shaft 82 but will only translate far enough for cam follower 164 to engage cam lobe 79, illustrated in FIG. 12, when a selector pin 60 and blade portion 64 are unlatched and engaged respectively into the groove 76 corresponding to six units of rotation. If the rack is in a plus rotate condition with rack teeth 126 engaging pinion 128, the cam surface 79 will cause cam follower 164 to rotate about the axis of shaft 110, thus causing pivotal rotating movement of rack switch spring 160. The engagement of rack switch spring 160 with the underside of rack at the point of the highest rise on the cam lobe 79, will cause rack 120 to change its position such that rack teeth 124 will engage pinion 128 and rack teeth 126 will disengage pinion 128. Cam lobe 79 is relatively position with respect to the other cam surfaces of rotate cam 68, to present its rise and dwell to cam follower 164, at a time corresponding generally to the beginning of the dwell in the translational motion of cam 68. Thus the rack is switched while there is substantially no translational movement of rotate cam 68 with respect to shaft 82. As the rotate cam 68 is rotated through the remainder of its 360 cycle, the cam 68 will translate in the opposite direction to its home position and thus be horned by zero rotate pin 92 engaging groove 70. Also any selector pins 60 will be restored to a latched position by the forces exerted thereon by cam rise 100 and cam dwell 102.

In order to provide the necessary motion to tilt print element 16 about its horizontal axis to present a particular row of characters in a particular printing position, simultaneously with the presentation of a selected column of characters being positioned in a printing position, thus providing a single preselected character, a tilt cam 68 of the configuration illustrated in FIG. 16 and its cam diagram illustrated in FIG. 17, is mounted coaxially on keyed shaft 82 for coaxial sliding motion thereon. Tilt cam 168 is formed with five grooves in the generally cylindrical exterior surface. Grooves 170 through 173 denote selection or tilt increment grooves. Groove 174 is the cam follower groove and has no translatory control over cam 168. To provide the mechanical input to the cam for the selection of a tilt increment, a latch and selector pin assembly such as illustrated in FIG. is provided with a composite of three latches and selector pins, one each for grooves 171, I72, and 173. The three selector pins '60 associated with the three grooves 171-173 are interlocked through a ball tube interlock 57 among themselves but are not interlocked with respect to the selector pin latch assemblies for the rotate cam 68. The tilt cam 168 has a home or zero tilt groove 170. A non-latching, spring-biased, homing selector pin 180 engages groove 170 to home the tilt barrel cam 168 in its zero tilt or home location and thus control the position of the printing element 16 in its zero tilt condition. Extending from the track 170 of cam 168 are camming surfaces 182 and 184. Camming surface 182 can be viewed in FIGS. and 16 and 184 in FIG. 10. The function of camming surfaces 184 and 182 are respectfully the same as the functions of camming surfaces 96 and 99. They provide a rise and fall for the spring biased homing and zero tilt selection pin 180 thereby allowing that pin to ride out of track 170 when a selector pin 60 and blade section 64 have been engaged with tracks 171, 172, or 173. The notation convention utilized with respect to the rotate cam 68 is likewise utilized with respect to the tilt cam wherein track 170 represents zero units of tilt. Tracks or grooves 171, 172, and 173 respectively correspond to one, two, and three units of tilt movement.

Track 174 provides a track for cam follower tab 186 which is formed as a part of bell crank 188. Bell crank 188 is pivotally mounted on supporting carrier frame 192 by pin 190. To provide an output of the motion picked up from the translatory movement of cam 168, bell crank 188 is provided with an output arm 194 which contains a connection 196 to tilt link 198. Tilt link 198 to output its motion, is pivotally connected to tilt ring 200 by pivot point 202. Tilt ring 200 is pivotally attached to yoke 132 by pivot member 204.

The tilting of the tilt ring 200 which carries type element 16 on the upper bail socket 206, is accomplished by selection of one of the selector pins 60 forcing the blade 64 into engagement with one of the tilt grooves 171-173 representing one, two. or three units of tilt. 0n the unlatching of one selection pin 60 in the pin block assembly corresponding to the tilt function. the homing or zero tilt selection pin 180 will be cammed up surface 184 and the tilt cam 168 will translate in a leftward direction as viewed in FIGS. 4 and 8. This left ward translation in response to the rotation of the cam 168 and further response to the rotation of shaft 82, causes cam follower tab 186, in FIG. 8 to translate leftwardly around pivot point 190. For example, if a letter is selected on keyboard 18 of FIG. 1, and that letter is positioned on type element 16 such that it requires a two unit tilt, selector pin 60 is unlstched by latch arm 48, acted upon by membrane 36 and shoe 44 in re sponse to a pneumatic signal from logic block 28. to cause blade portion 64 to drop into groove 172. As groove 172 is progressively rotated past blade 64, cam

168 will laterally translate along shaft 82 in a leftward direction by an increment corresponding to the increment required for a two unit tilt movement. This movement being picked up by cam follower tab 186 causes bell crank 188 to rotate in a generally counterclockwise direction around pivot point 190 as viewed in FIG. 8. This causes output arm 194 and swivel connection 196 to pull tilt link 198 in a generally upward direction as viewedin FIG. 8. The upward direction of link 198 in FIG. 8 corresponds to a generally down and leftward direction of movement for link 198 as viewed in FIG. 9. The downward and leftward movement of tilt link 198 translated through pivot pin 202 causes tilt ring 200 to rotate in a clockwise direction around pin 204. Upper ball socket 206 is connected to lower ball socket shaft by conventional means well known in the IBM SELECTRIC typewriter.

As tilt ring 200 rotates about pivot pin 204, upper ball socket 206 is carried therewith thus oreinting print element 16 such that the appropriate circumferential row of type characters are presented at the appropriate print line.

To provide accurate vertical placement of the selected row of characters, a tilt detenting mechanism is provided. The tilt detent mechanism comprises a series of detent notches 206 respectively corresponding to the angular position of the tilt ring 200 for proper positioning of each of the four rows of characters on typehead 16. These detent notches 206 are formed into an arcuate lower surface of tilt ring 200. Referring to FIG. 2, tilt detent 208 is formed as a part of tilt detent lever 210. Tilt detent lever 210 is spring biased by spring 212 to be normally engaged, through tilt detent 208, with one of the plurality of detent notches 206. Detent crank 214 is pivotaily mounted on yoke 132 by means of a mounting pin or screw 216. Detent lever 210 has a pivot point at pivot means 218. Detent lever 210 has a depending leg 211 which is in turn engageable by crank 214. The movement of crank 214 around pivot point 216 engages depending leg 211 of detent lever 210acting against the bias of spring 212 to withdraw the detent 208 from detent teeth 206 and allow free movement of the tilt ring 200 in response to the tilt ring 198. As an ancillary function, the withdrawal of detent 208 from detent teeth 206 also acts to move rotate detent 218 downward, as viewed in H6. 9, to remove the detent surface 220 from the detent teeth of type element 16. This allows the rotation of type element 16 in response to the rotate selection mechanism.

Crank 214 is moved pivotaily around pivot point 216 in response to forces exerted on it by cam follower 222. Cam follower 212 is pivotally mounted to the frame of the carrier 192 by pivot 224. Cam follower 222 has a follower tab 226 which engages detenting cam 228 keyed to and mounted on rotary force receiving print sleeve 230. Print sleeve 230 is positively driven rotationally by print shaft 232.

To transmit the torque from print shaft 232 and print sleeve 230 to the keyed shaft 82, a gear 234 is fixedly attached to print sleeve 230. Gear 234 is engaged through idler gear 236 which is mounted on carrier frame 192 with cam shaft drive gear 238. Cam shaft drive gear 238 is fixedly attached to cam shaft 82 upon which tilt barrel cam 168 and rotate barrel cam 68 are slideably mounted. The print sleeve 230 may be described as the power receiving means and the gear train keyed shaft and cams together with linkage driven by the cams translation may be described as the power utilizing means.

To impart the necessary arcuate impacting movement for printing, to type element 16, and yoke assembly 132, rocker assembly 116 must be moved pivotally about pivot points 118. This is accomplished by transmission of a short duration force being applied to the rocker assembly 116. This force is applied through a stud member 250 in FIG. 3. The force is provided to stud member 250 by print cam follower 252 which in turn is pivotally mounted at pivot 254 to carrier frame member 192. Print cam follower 252 further includes a cam roller 256 which is in rolling engagement with print cam 258. Print cam 258 has a high lobe for imparting movement through print cam follower 252 to stud 250. Print cam 258 is keyed to and rotates with print sleeve 230 which in turn is powered by intermittently rotating print shaft 232.

Print cam roller 256 is, in addition to being rotatably mounted on the end of print cam follower 252, slideably mounted upon mounting pin 260 for translational movement along the axis of pin 260.

To provide a means for shifting print cam follower roller 256 out of engagement with the 258 to produce a non-printing condition the slide member 262 is provided with a multiple latching control. A latch member 264 presents a flat force surface 266. Flat force surface 266 is in contacting arrangement with plunger 268 of pneumatic actuator 270. Biasing spring 272 retains force surface 266 in contact with plunger member 268. Latch member 264 also acts to move latch 274 by physical interference therewith, and thus withdraw both their respective pawls from the latching surface 276 of slide member 262. Spring member 278 provides a constant bias on follower arm 280 and thus on slide member 262 which is engaged by follower arm 280. Slide member 262 has upturned tab shift yoke member 282 which straddle the print cam follower roller 256. Any movement of slide member 262 is thereby translated into a corresponding lateral translation of print cam follower roller 256. With the withdrawal of latch members 264 and 274 from latching surface 276, slide member 262 is thereby freed to translate leftward as in FIG. 7 thus moving cam follower roller 256 out of engagement to the left and away from the cam rise of print cam 258. This lateral translation of roller 256 out of engagement with any of the cam lobes of cam 258 has the effect of disconnecting the motion normally accorded print cam follower 252, due to rotation of print shaft 232 and print cam 258.

To restore slide member 262 to its normal operating position, follower arm 280 is provided with a cam follower lug 286. This cam follower lug is acted upon by restore cam 288 which is in turn mounted upon and rotates with print sleeve 230. The rotation of the print shaft 232 and the print sleeve 230 causes the restore cam 288 to engage cam follower stud 286 and thus move follower arm 284 thus pushing slide member 262 rightward restoring the print cam follower wheel 256 to its normal operative position.

To normally cause escapement of the carrier with respect to the print line, and an escapement cam 300 is rigidly fixed to print sleeve 230, as illustrated in FIGS. 6 and 8. Escapement cam 300 rotates with print sleeve 230 and print shaft 232. Escapement cam follower 302 in the form of a bell crank. is provided with a follower wheel 304 in engagement with the periphery of escapement cam 300. Escapement cam follower 302 is pivotally mounted on a pivot pin 306 which in turn is supported by carrier frame member 192. Pivotally attached to the other arm of the cam follower bell crank 302 at pivot point 308, is escapement link 310. Escapement link 310, escapement follower bell crank 302, and escapement follower wheel 304 are all biased into a position, whereby escapement follower wheel 304 is in engagement with periphery of escapement cam 300, by means of a spring 312. Escapement link 310, includes depending and upstanding tabs 314 and 316 respectively. Depending tab 314 of escapement link 310 engages escapement pawl tab 316 which is formed on the end of the escapement pawl 318. This is to provide a means for extracting the escapement pawl from the escapement rack to cause escapement of the carrier with respect to the print line. The addition of tab 316 to escapement pawl 318 is a modification made to the escapement pawl assembly as disclosed in US. Pat. No. 3,l26,998 issued to L. E. Palmer.

Ajacent the normal position of the escapement link 310, is located a pneumatic or equivalent actuator 318. Pneumatic actuator 318 has a plunger 320 which extends under air pressure being introduced into pneumatic actuator 318 through inlet port 322 from the logic block 28. The extension of plunger 320 will displace escapement link 310 laterally to disengage depending tab 314 from escapement pawl tab 316 and trap the escapement link 310 in its displaced position by spring 317. With the disengagement of depending tab 314 from escapement pawl tab 316, any movement of the escapement linkage will be ineffective to cause escapement.

DESCRIPTION OF OPERATION A better understanding of the mode of operation of the invention will become apparent from the detailed description of the operation of the invention described below.

Referring particularly to FIG. 1, upon the initiating of a key stroke at the keyboard 18 of typewriter 12, necessary signals will be generated and transmitted through signal carrying member 20 to the print carrier 10. The signals will be utilized at the carrier and selection will occur within the carrier 10 thus rotating and tilting print element 16 to present the preselected character to writing page 24 against platen 12 in response to the rotation of print shaft 14.

Referring now to FIG. 20, upon the depression of a key member of the keyboard 18, a keyboard signal generator 26 generates an electrical, or pneumatic signal representing that character. These signals are then transmitted to a logic block 28 where the signals are decoded and recoded providing m outputs. The number of the outputs is dependent upon the number of functions that are to be effected as a result of direct signals from the logic block. The signals are split, some of the signals going to an actuator block 30 where each signal from the output block is received and utilized to actuate a mechanical mechanism for further control of the typehead l6 and carrier 10. In this particular example, actuator block 30 will receive nine signals, one for each of the three tilt selection latch/selection pin assemblies and one for each of the six rotate selection latch/selection pin assemblies. Additional signals for dead key, no print, and rack switch are routed directly from the logic block to the appropriate transducer on the carrier to 13 effect those functions. Other signals may be provided as needed or desired.

As a result of the outputs of logic block 28, two sig nals will be received at the actuator block in a form which will activate appropriate tilt and rotate selection latches 48 and selection pins 60. For the sake of understanding specific examples will be used but the reader will fully appreciate that the process in general is the same regardless of the position of the printhead desired, and that the operation of the carrier is substantially the same for analogous cases with only different pins being selected as a result of different signals being received in the inlets 42 to the pneumatic actuators for the latch levers 48 of the pin selection mechanism.

By way of example, the operator of the typewriter selects the letter lowercase r by depressing the keybutton corresponding to r. This generates signals which are passed through logic block 28 and result in output signals from the logic block in the form of two pneumatic pulses. One pneumatic pulse is directed to the selector pin 60 corresponding to groove 74 in rotate cam 68. The other pneumatic pulse is outputed through the actuator block 30 and latch assembly corresponding to the selector pin 60 mating with tilt groove 172 of tilt cam 168. The pulses are received in inlet port 42 of actuator block 30. The pressure in chamber rises sharply distending diaphragm 36 and applying a force onto shoe 44 thus forcing latch lever arm 48 in a clockwise direction around pivot point 50. Rocking latch lever 48 in a clockwise direction withdraws latching surface 54 from latching surface 58 of selector pin 60. Under the influence of compressed spring 62, blade 64 extends into groove 74 of rotate cam 68. Following an identical analysis of the action of the parts, selector pin 60 and blade 64 will extend likewise into groove 172 of tilt cam 168. The depression of the print key corresponding to the letter r through well known techniques, acts to release a single cycle clutch (not shown) to cause the print shaft 232 to begin to rotate. As print shaft 232 rotates. print sleeve 230 rotates therewith causing gear 234 to rotate. The angular motion of gear 234 is transmitted through idler gear 236 in matched relationship therewith, to the driven gear 238. Gear 238 is fixedly attached to keyed shaft 82. Thus the rotation of gear 238 causes rotation of shaft 82. Inasmuch as the keying of shaft 82 is complimentary to the keyed core or holes through the centers of tilt cam 168 and rotate cam 68, tilt cam 168 and rotate cam 68 revolve with keyed shaft 82. Selector pins 60, having previously been inserted under the influence of compressed springs 62, into grooves 74 and 172 respectively, the rotate and tilt cams begin a lateral displacement in cor respondence to the displacement of the cam grooves 74 and 172. The rotate cam 68 and the tilt cam 168, translate on shaft 82 generally in opposite directions and toward their respective ends of keyed shaft 82. This direction of translation of each cam 68, 168 prevents an interference in the center of the shaft 82.

Inasmuch as rack member 120 is oriented with rack teeth 124 engaging the teeth at pinion 128, and this condition has been arbitrarily designated as a minus rotate condition, the movement of the rotate cam 68 will cause a translation of rack 120 with respect to the carrier frame 192. That translation, since pinion 128 is fixed spacially with respect to the carrier frame 192, will cause rotation of the pinion 128 in a clockwise direction when viewed from above. As rotate cam 68 ro- 14 tates about the axis of shaft 82, tilt cam 168 is likewise rotating in synchronous motion therewith.

Inasmuch as a selector pin 60 has been inserted into groove 172, as tilt cam 168 rotates the cam will trans late a distance corresponding to two units of tilt of the printhead 16 during the course of approximately one half revolution of the cam. This translation causes groove 174 to likewise translate in a leftward direction as viewed in FIG. 8. As groove 174 translates leftward, cam follower tab 186, a part of tilt bell crank 188, will translate leftward thus pivoting cam follower tilt bell crank 188 about pivot point 190. This motion will act to rotate follower bell rank arm 194 in a counterclockwise direction thus pulling, through connection 196, the tilt link 198 in a generally upward direction as viewed in FIG. 8.

Referring now to FIG. 9, the motion of tilt link 198 referred to immediately above, corresponds to a down ward leftward motion of tilt link 198. This extension of tilt link 198 acting through pivot pin 202 causes tilt ring 200 to rotate in a clockwise direction around pivot pin 204. This rotation of tilt ring 200 around pivot pin 204 is permitted by the extraction of tilt detent 208 from detent notches 206. The extraction of detent 208 from detent notches 206 is accomplished by the timed relation of cam 228 which is directly driven by print shaft 232 through print sleeve 230. The rise and high dwell of cam 228 acts through follower stud 226 to rock the follower 222 about pivot 224. The rocking of follower 222 about pivot 224 acts through detent crank 214 and pivots it about its pivot point 216. The pivoting of detent crank 214 around 216 engages depending leg 211 of detent latch member 210. The exertion ofa force by detent crank 214 through detent latch leg 21] rotates detent latch 210 about pivot point 218 against the force of spring 212 and lowers the detent 208 out of the detent teeth 206 in tilt ring 200. This frees the tilt ring 200 for relatively free moving motion about pivot point 204. The high dwell of detent cam 228 is formed and positioned to allow the entire tilting operation to occur and to maintain detent member 208 out of engagement with detent teeth 206 except at that point in the cycle where the head is to be detented in a particular position for printing. At all other times of the cycle, the high dwell of detent cam 228 acts through the above described linkages and relationships to remove and keep removed from detent teeth 206, the detent 208. As detent cam 228 rotates during the printing cycle, the low dwell will allow detent cam follower 222 to swing out of the way from detent crank 214 thus releasing the forces against pending leg 211 of detent member 210. Spring 212 being feed to act, will then pull detent 208 into engagement with the appropriately alined detent teeth 206. This immediate sequence of operations will occur just prior to the actual printing operation where rocker 116 is pivoted about its pivot pins 118 to impact typehead 16 into printed page 24. After printing, tilt detent 208 is extracted from the detent tooth 206 as described earlier to allow the head to be returned to its home position in response to the continued operation and revolution of tilt cam 168. The detenting operation occurs generally during the stationary dwell time as illustrated in FIG. 17 as that time between approximately l of rotation and about 245 of rotation of the tilt cam. The above sequence is that of the motion converting and transmitting means to convert and transmit the motions of cams 68 and 168 to rotate and tilt motions of typehead 16.

Simultaneous releases result from the extraction of detent 208 from detent teeth 206. Rotate detent 218 is forced down against the force of spring 219 by detent 208, to retract detent surface 220 from the detent teeth of print element 16. Rotate detent 218 will remain ex tracted from the detent teeth of print element 16 as long as the tilt detent 208 is extracted from the tilt detent teeth 206. Thus the typehead 16 has been simultaneously freed for restoration to its home position both in the tilt and the rotate axes.

As both the rotate and tilt cams are rotated past the high dwell region, the descending slopes of the respective grooves 74 and 172, cause translation of the two cams 68 and 168 toward each other and back toward their respective home positions. As they return to their home positions. homing pins 92 and 180 ride down de scending cam slopes 99 and 182 respectively to reposi tion their tips within the homing tracks 70 and 170 of cams 68 and 168 respectively. The reverse translational movement of the rotate cams acting through cam following tab 88 and cam follower 90, forces rack tab 114 and rack 120 with rack teeth 124 in engagement with pinion 128 to reverse its rotation and return the head 16 through four increments of rotate in the opposite direction from which it had originally been displaced. Likewise as the tilt cam is completing its rotation, the homing pin 180 engages slot 170 or groove 170 and re tains the tilt cam in its home position. As the tilt cam is returned to its home position, cam follower tab 186 is forced to the right as observed in H0. 8 thus rotating Cam follower bell crank 188 in the opposite direction to which it had previously been rotated and extending tilt link 198 in a downward direction. The downward direction corresponds in FIG. 9 to an up and to the right motion thus returning pririthead 16 and tilt ring 200 to its home or zero tilt position. As this time the detent member 208 remains out of teeth 206 and detent member 218 and detent surface 220 remain out of engagement with the detenting teeth on the periphery of the lower edge of typehead 16.

A typehead carrying 96 characters in four rows will of necessity have 24 columns of characters. The 24 columns of characters are divided into upper and lower case of 12 columns each. In each case, there have been designated for the sake of reference a zero row and six rows of negative or minus rotation and five rows of positive or plus rotation.

In the event that the letter lower case s is selected. its position on the typehead is such as to require a two increment tilt, the same as the lower case r used in the immediatie preceding example. The lower case 5 also requires four units of rotate but unlike the lower case r used above, the lower case s requires four units of plus rotate as opposed to four units of minus rotate.

With respect to the operation of the tilt bell crank cam follower 188, tilt link 198, tilt ring 200, and detenting 206, 208, 218, and 220 of the typehead, the operation is exactly identical in both cases and will not be repeated here.

However, with respect to the rotate function, inasmuch as there are only six units of rotate provided for in the rotate cam 68, it is necessary to reverse the rotation of the typehead 16 in response to an additional signal. A signal indicating a positive rotate is derived from the logic block 28 in the form of a rack switch signal.

The rack switch pulse is a direct output of the logic block 28 to a rack switch bellows assembly 138. AS part of the pneumatic or other equivalent inputs to the print carrier, a pneumatic pulse is received through input conduit 144 through bellows block 142 into chamber 146. Distendable diaphragm 148 is forced to balloon outward from chamber 146 thus forcing bellows member 150, FIG. 9, to pivot around its pi vot point 152. Rack switch bellows tab 140 being part of bellows member 150, is forced downward and engages rack tabs 136 The force exerted by the pneumatic pulse introduced to rack switch bellows 138, forces rack tab 136 downward rotating rack 120 about pivot shaft 122. The effect is to disengage rack teeth 124 from the teeth of pinion 128 and simultaneously to engage rack teeth 126 with pinion 128. The effect of this is to create a reverse rotation to that described previously with the same translational direction of rack 120. As cam follower tab 188 is forced laterally by the rotation of cam 68 and its lateral displacement due to a selector pin 60 being dropped in the four unit groove 74, rack 120 is translated laterally four units of rotation displacement, by the forces exerted on rack tab 114 by cam follower 90. During the period of dwell during the rotation of cam 68, printing occurs after detenting of the type element 16 as previously described. After printing, the typehead and tilt ring are released by their appropriate detents 218, 208 and the tilt and rotate cams 168, 68 are cammed back to their home position. Upon return to their home position and during the final phases of rotation, cam lobe 77 illustrated in FIGS. 13 and 14 is presented to follower arm 166. As follower arm 166 is engaged by cam lobe 77, it is rotated about shaft in a counterclockwise direction as viewed in FIG. 9. The effect of this is to rotate rocker 162 and spring 160 in a movement counterclockwise and concentric to shaft 110. As spring 160 is rotated counterclockwise it engages the lower portion of the rack approximately directly below rack teeth 124. As a result of this force, rack 120 is shifted such that rack teeth 124 again engage pinion 128. This operation is accomplished upon the return to home position of rotate cam 68 after any operation of the print carrier which places the rack 120 in what has been referred to a plus rotation configuration. The plus rotation configuration is anytime that rack teeth 126 are engaged with pinion 128. Thus at the completion of any print cycle. the bifurcated rack 120 is restored to a negative rotation mode prior to the initiation of any subsequent print cycle.

In both of the above examples, the rotation of the print and tilt cam 68, 168 toward their home position after completing all translatory motion. causes blade 64 of selector pin 60 engaged with both grooves 74 and 172 of the rotate cam 68 and tilt cam 168 respectively, to follow the profile of the cam illustrated as cam profile 102 in FIGS. 10 and 1]. The effect of the radial cam rise on these profiles is to force selector pin 60 radially away from the axis of the rotate cam 68 and tilt cam 168. Upon sufficient forcing of said selector pins 60 radially away from said axis, the spring action of tension spring 52 acting on latch lever 48 will cause latch lever 48 to rotate in a counterclockwise direction about pivot point 50. This presents latching surface 54 in a position to engage latching surface 58 when blade member 64 is no longer engaged by the rise 102 of either cam 68 or 168. This immediately above described sequence effectively resets each and every latch pin 60 

1. A selection mechanism for a printer of the single element type, having a single print element carried by a print carrier, comprising: a multicam surfaced rotational barrel cam rotationally and slideably supported for rotational movement and axial movement with respect to said carrier; at least one selectably operable follower means spacially fixed with respect to said carrier for selective engagement with one of said surfaces; means for creating motion between said selected follower means and said selected cam surface to create cam controlled motion of said cam with respect to said carrier; said motion comprising an axial translation and reverse axial translation from and to a predesignated position; first means for transmitting said motion of said cam to a second means cooperating with said print element for converting said cam controlled motion of said cam into a selected directional rotational motion of said type element, thereby producing the selected rotation of said element in one of two selectable directions from an original at rest position, said selected rotation resulting from a single axial directional motion of said cam with respect to said follower means.
 2. The selection mechanism of claim 1 wherein said second means for converting said controlled motion into a selected directional rotational motion further comprise: a pinion drivingly associated with said element, and a bifurcated rack means switchable between alternate engagement of each of the rack portions thereon, to produce alternatively two directions of rotation of said pinion from otherwise identical axial displacement of said cam.
 3. The selection mechanism of claim 2 wherein said mechanism further comprises: means to effect the disengagement of one portion of said bifurcated rack means and the engagement of the other portion thereof.
 4. The selection mechanism of claim 3 wherein said means to effect the disengagement, further comprise meAns controlled by said cam to effect said disengagement and for causing engaging of said other portion of said rack at a point where said rack is displaced axially with said cam to its most extreme point of travel, thereby effecting an additional rotation of said pinion during said reverse axial translation, to position said element at its home row position one-half revolution from said predesignated position.
 5. A rotate selection mechanism for selection of characters on a single element print member comprising: a multisurfaced barrel cam; a cam selector mechanism for selective engagement with a selected one of said surfaces of said cam to effect an axial displacement of said cam and translation with respect to said selector mechanism, said displacement for each of said surfaces being proportional to the rotation of said print member required to position a column of characters thereon in a position to print one of said characters; a follower means to pick up and transmit to rack means the axial translational motion of said cam said follower drivingly associated with said rack means, said rack means having two racks; a pinion drivingly connected to said print member; said rack means associated with said pinion and adapted to be shifted to engage one of said racks with said pinion for transmitting said follower motion to said pinion to cause rotation thereof up to a maximum of about one-forth of a revolution of said pinion and said print member during the maximum displacement of said cam follower means, and racks; selectively activatable means for engaging a selected one of said racks with said pinion to produce selective directions of rotation of said print member from identical axial displacement of said cam.
 6. The selection mechanism of claim 5 further comprising rack switching means for shifting said rack engagement to the other of said racks in timed relation to the movement of said cam and at a point in the rotation of said cam where said cam has been displaced to its maximum axial displacement, and after having caused the print member to rotate in one preselected direction, thereby causing continued rotation of said element in said direction during restoration of said cam to its nominal position, producing a complete one-half revolution of said element thus effecting case shift.
 7. A selection device for a single element printer having a single print element, comprising: a multichannel barrel cam supported for rotation about and translation along its axis; a plurality of fixed selection pins each selectively engageable with one of said channels; a cam follower to transmit the axial translation of said cam; a pinion; a switchable member having two racks for alternative engagement with said pinion and engaged with said follower for movement therewith, for converting said translation to controlled rotary motion of said pinion, said pinion drivingly engaged with said element to effect rotation thereof; a selectively actuable switching member or selectively switching said rack for reversing the direction of rotation of said pinion in response to the translation of said cam; means for restoring said switchable member to a first condition of engagement upon the completion of a complete rotation of said cam; and cam profile and follower means to effect the restoring of said switchable member to said first condition at a point where said cam has translated the maximum distance capable and where said switchable member was in other than said first condition during said cam translation. 